Luciferase

Luciferases are enzymes that emit light. A diverse group of organisms use
luciferase-mediated bioluminescence to startle predators or to attract prey or mates. The
luciferase from the North American firefly releases green light during the oxidation of
its chemical substrate, luciferin. Other organisms, including plants, that express the
luciferase (LUC) gene will also glow faintly green when supplied with luciferin.

The glow is widely used as an assay for LUC expression, which acts as a
"reporter" for the activity of any regulatory elements that control its
expression. Luciferase is particularly useful as a reporter in living cells and
organisms. LUC gene fusions provide a "window" on to the mechanisms that
regulate the activity of specific genes, in specific, living cells. Our interest is in the
mechanism of rhythmic regulation in higher plants: a rhythmically-expressed luciferase
reporter is one of our principal tools. Images of bioluminescence from our CAB:LUC
Arabidopsis plants are shown at the top of this page (the cotyledons of two seedlings) and
on the front page (an older, rosette plant).

The LUC+ gene from Promega Corporation is an order
of magnitude brighter in Arabidopsis and has no disadvantages in other
species, so we now use this routinely. The protein is cytoplasmic, whereas the
native LUC is peroxisomal.